Could someone please tell me if I should be using magnum primers in my 7mm Rem Mag when reloading?

Some publications only seem to use them on the slower powders whilst others like the Speer reloaders handbook uses them on all powders, fast or slow.

I am currently developing a load using Hornady`s new 139 gn SST projectiles and, using Hodgdon 4831sc with magnum primers up to a max of 66gns the groupings were awful (no pressure signs).

I know it is not the rifle as it shoots 3/4moa with Remington 150 corelokts.

I am thinking of trying a local powder here (ar2209) which is the equivalent of IMR4350 with this projectile and was wondering if I should stick with magnum primers on this faster powder?

Any advice would be appreciated.

H-4831 From 64.0 grains to 71.4 grains
CCI-200 Primer

Your load is on the light side...

AR-2209 From 49.0 grains to 59.0 grains
CCI-200 Primer

If you decide to switch powders.

I found IMR-7828 From 60.1 grains to 72.1 grains
CCI-200 Primer to be best with the 139 grain bullet.

I use those Hornaday 139 gr SST in my 7mm Mag w/ 7828 like the aforementioned w/ CCI magnum primers and it shoots a wonder.

Sometimes you'll get better accuracy with standard primers over mag. I don't hunt in extremely cold weather so that I may need a hotter primer. I usually shoot 66.5 grains of H4831 with 162 Hornady's and Fed10M's. No problems and very accurate.

Bob257

IMR 4350 seemed to be the most accurate powder we found when working up a load for our 7mag.

Like Huntaholic I have found that my best accuracy in both my 7MM Remingtons comes with IMR4350. I use Magnum primers CCI, Federal and Remington and don't see much change there.

Gentlemen,

I use IMR 7828 almost exclusively in my 7mm RM, and always use Magnum primers. I have found that velocities are much more consistent with magnum primers than with standard primers. 7828 and the 139 gr. SST is a dynamite combination.

Joel Slate
Slate & Associates, LLC
www.slatesafaris.com

7mm Rem Mag Page www.slatesafaris.com/7mm.htm

I've used H4831, IMR 4350, IMR 7828, RL22 all with good sucess.

I generally used Fed 215 mag primers but occasionally used standard primers.

Many thanks Gentlemen,

It would appear that my loads so far are a little light so I will continue with the H4831 and Ar2209 and see which comes up best.

Happy hunting to all of you.

For my pure accuracy load I've always used 210's and I4350. Either the 139's or the 154's. FWIW, Dutch.

When using the slow burning powders like RL 22 or 4831 it's best to use Mag primers like Federal Match 215GM and for the Med burners like RL 19 or IMR 4350 the Fed Match 210GM will work great, and provide the best accuracy.

I myself use Fed Match 215GM for all my loads and IMR 4350 @ 61.0 with 160 Noslers.